Note: Descriptions are shown in the official language in which they were submitted.
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CALL INFORMATION OUTPUT IN A TELECOMMUNICATION NETWORK
The present invention relates to a method and apparatus
for outputting call information in a telecommunication
network.
In telecommunication networks such as fixed access
networks and cellular radio telephone networks there is
usually a need to record call information at at least
one exchange of the network. This information may
IS include the identity of a caller (A-number), the
identity of the called party (B-number), and the
duration of a call. In cellular radio telephone
networks, the recorded information may also include the
International Mobile Subscriber Identity (IMSI) code of
the Subscriber Identity Module (SIM) used with the
calling mobile telephone, and the International Mobile
Equipment Identity (IMEI) code of the calling telephone
itself. Both the IMSI and IMEI codes are typically sent
by a mobile telephone to the cellular network during a
2~ call set-up phase. For a given call, a record stored in
an exchange is normally output to a centralised billing
system of the network upon termination of the call.
Historically, this record has been referred to as a
''Toll Ticket" (TT) although more recently the term "Call
Data Record'' (CDR} has been used.
US5,506,893 describes a telecommunication network in
which a CDR is output from a switching centre to an
external billing system upon termination of a call.
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According to a first aspect of the present invention
there is provided a method of providing information
relating to a telecommunication call, in a
telecommunication network, to a data storage system, the
method comprising:
receiving caller identity information at an
exchange of the network during a call set-up procedure
l0 between a calling device and the exchange, and storing
the information at least temporarily at the exchange;
sending an incoming call alert message to a called
device;
prior to receiving a call answer message at the
1~ exchange, or in direct response to receipt of a call
answer message, outputting from the exchange to said
data storage system a Call Data Record containing at
least the received caller identity information.
20 Embodiments of the present invention provide for the
output of call information at a very early stage in a
call, i.e. immediately following the answering of the
call or during the call set-up phase. This makes
possible, for example, real-time billing and fraud
25 detection prior to or during a call.
In certain embodiments of the present invention, the
telecommunication network comprises a cellular radio
telephone network and the call is made from a cellular
30 radio telephone device. The exchange from which the
call information is output is then the Mobile Switching
Centre (MSC). The information may include at least one
of the subscriber telephone number, IMEI code, IMSI
code, or B-number.
In other embodiments of the present invention, the
telecommunication network comprises a fixed access
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network in which telephone device is coupled to the
exchange via land lines. The information output by the
exchange preferably includes the caller's telephone
number (A-number) and the called number (B-number).
According to a second aspect of the present invention
there is provided apparatus for providing information
relating to a telecommunication call, in a
telecommunication network, to a data storage system, the
apparatus comprising:
first receiving means far receiving caller identity
information at an exchange of the network during a call
set-up procedure between a calling device and the
exchange, and for storing the information at least
temporarily at the exchange;
transmitting means for transmitting an incoming
call alert message to a called device;
second receiving means for receiving, in the event
that the called device answers or otherwise accepts the
incoming call alert, a call answer message sent to the
exchange; and
output means for outputting, prior to, or in
response to, receipt of said call answer message, from
the exchange to said data storage system, a Call Data
Record containing at least the received caller identity
information.
Preferably, said first and second receiving means, said
transmitting means, and said output means are provided
as an integral part of the network exchange. Where the
network comprises a cellular radio telephone network,
the exchange is a Mobile Switching Centre (MSC). The
MSC may be contained within a housing which is
physically spaced apart from an external billing system
which is arranged to receive the Call Data Record output
by the MSC. More preferably, a plurality of MSCs are
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arranged to provide the output CDRs to a common external
billing system.
According to a third aspect of the present invention
there is provided a telecommunication network having a
plurality of interconnected exchanges for routing calls
in the network, and a common billing system coupled to
each of said exchanges, each exchange comprising:
first receiving means for receiving caller identity
information during a call set-up procedure between a
calling device and the exchange, and for storing the
information at least temporarily at the exchange;
transmitting means for transmitting an incoming
call alert message to a called device or to a called
device via one or_ more further exchanges;
second receiving means for receiving, in the event
that the called device answers or otherwise accepts the
incoming call alert, a call answer message sent to the
exchange; and
output means for outputting, prior to or in
response to receipt of said call answer message, from
the exchange to a data storage system, a Call Data
Record containing at least the received caller identity
information.
For a better understanding of the present invention and
in order to show how the same may be carried into effect
reference will now be made, by way of example, to the
accompanying drawings, in which:
Figure 1 shows schematically a telecommunication
network including a cellular radio telephone network;
Figure 2 is a flow diagram illustrating the method
of operation of the telecommunication network of Figure
1; and
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Figure 3 illustrates an external billing system
shared by a number of Mobile Switching Centres of a
cellular radio telephone network.
5 D . ai l Pd D srri nt i on of Emhodi menu
There is shown in Figure 1 a telecommunication network
comprising a Global System for Mobile Communications
(GSM) cellular radio telephone network and a fixed
access network. The former consists of a Mobile
Switching Centre (MSC) 1, a set of Base Station
Controllers (BSC) 2 only one of which is shown in Figure
1, and a set of Base Transceiver Stations (BTS) 3 again
only one of which is shown in the Figure. The MSC,
IS BSCs, and BTSs provide functionality as defined in the
relevant European Telecommunications Standards Institute
(ETSI) GSM standards.
In the GSM network; mobile stations such as that
2o indicated by reference numeral 4 communicate with a BTS
3 over the air interface. User data and signaling
messages are coupled between the BTS 3 and the MSC 1 via
the BSC 2., The MSC 1 acts as an exchange of the GSM
network, routing calls between a mobile station 4 and a
25 called, or calling, station.
In the example of Figure 1, the destination of a call
from the mobile station 4 is a land line telephone 5
which belongs to a subscriber of a fixed access network
30 6. A call may be routed through several intermediate
exchanges (e. g. in the case of an international call)
and may also pass through several exchanges of the fixed
access network, although for the sake of clarity these
exchanges are not shown in Figure 1. In the same way,
35 it will be appreciated that a call may be routed through
several MSCs 1 en route from the mobile station 4 to the
fixed line telephone 5.
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The mobile station 4 is provided with a Subscriber
Identity Module (SIM) 7 which contains a solid state
memory arranged to store a unique International Mobile
Subscriber Identity (IMSI) code. The mobile station 4
itself has a solid state memory arranged to store a
second unique code known as an International Mobile
Equipment Identity (IMEI) code. The form of these two
codes is defined in the relevant GSM standard.
When a user of the mobile terminal 4 places a call to
the fixed line telephone 5 by dialing the B-number of
that telephone, at least the IMST code and the telephone
number (A-number) assigned to the mobile terminal 4 are
transmitted to an input/output device 8 of the MSC 1 on
a signaling channel of the GSM network (the IMEI code
may or may not be sent at this stage). In response to
the call request, the MSC 1 first verifies the right of
the mobile terminal 4 to use the services of the GSM
network on the basis of the A-number and the IMSI code
(e.g. using a database of subscribers of the GSM
network) .
Assuming that the mobile terminal 4 receives
authorisation from the MSC 1 to place the call, the MSC
1 transmits an incoming call request from an
output/output device 9 to the fixed line telephone 5 via
the fixed access telephone network. A signaling
protocol such as the Signaling System 7 (SS7) is used to
relay the request between the MSC 1 and the various
exchanges. When the request reaches the fixed line
telephone 5, the phone rings in the normal manner.
If the call is answered at~the fixed line telephone 5,
then a call answer message is returned to the fixed
access network 6, either by the telephone 5 or by some
intermediate device, e.g: a concentrator. The call
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answer message is also transmitted back to the
input/output device 9 of the MSC 1 of the GSM network,
again using the SS7 signaling protocol.
Connected to the MSC 1 of the GSM network is a so-called
input/output group device or external billing system 10.
This may be a personal computer (PC), work station, data
storage device or the like, which logs information
concerning calls switched by the MSC 1. The information
recorded by the external billing system 10 enables the
operator of the GSM network to charge subscribers, trace
calls, and identify calls made from "illegal'' equipment.
The latter is achieved using the transmitted IMSI code
and also the IMEI code (if transmitted).
When the call answer message is received by the MSC 1
from the fixed line telephone 5, the MSC 1 provides a
traffic channel (:i.e. voice or data) to the mobile
station 4 enabling the mobile subscriber to communicate
with the fixed line telephone. In addition, receipt of
the call answer message causes the MSC 1 to output to
the external billing system 10, via an input/output
device 11, the caller's A-number, IMSI code, the called
party's B-number, and the call start time. This data is
in the form of a partial Charging Data Record (CDR) and
is recorded by the external billing system 10. When the
call is terminated by one of the parties to the call
hanging-up, a call termination message is received by
the MSC, and a call end time output to the input/output
group device 10 to complete the partial CDR.
Figure 2 is a flow chart illustrating the method of
operation of the network of Figure 1, and relates in
particular to the output of the CDR to the external
billing system 10.
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The external billing system is physically separate from
the MSC {1) which is usually contained within a single
large housing. By transferring the partial CDR, upon
receipt of the call answer message from the B-
subscriber, to the external billing system the network
operator is able to access the record at an early stage
in a call for the purposes already set out above.
The external billing system is typically shared by a
number of MSCs 1 of the GSM network. This is
illustrated in Figure 3.
It will be appreciated by the person of skill in the art
that various modifications may be made to the above
described embodiment without departing from the scope of
the present invention. For example, the exchange from
which the CDR is output may be an exchange of a fixed
access network rather than that of a cellular radio
telephone network. In another modification, the partial
CDR is output from the exchange to the external billing
system during the call set-up phase, i.e. prior to the
call answer message being received at the exchange from
the B-subscriber. The CDR provided to the external
billing system may include additional information such
as the MSC identity, and the originating/terminating
cell identity (Cell Global Identity) in the GSM network.
